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+--- Thread: Issue with the Apple LLVM compiler 3.0... (/thread-9606.html)
Issue with the Apple LLVM compiler 3.0... - Jamie W - Dec 8, 2011 10:48 AM
Hello,
Is anyone else having issues with the Apple LLVM compiler 3.0? (iOS Xcode 4.2).
I've just had (something like) the following C++ code running:
void
Class::Function()
{
WORD Var;
Var = m_Var++;
// do something with Var..
}
Okay, so m_Var is a member of class 'Class'.
When I run this code, compiled with the Apple LLVM compiler 3.0, Var is set, but m_Var is not incremented.
When I switch to the LLVM GCC 4.2 compiler, it works (is incremented).
What's going on? Is the Apple LLVM compiler 3.0 buggy?
RE: Issue with the Apple LLVM compiler 3.0... - Jamie W - Dec 8, 2011 12:21 PM
Just to expand a little...
It all works fine when I compile with GCC (arm6 and arm7) or LLVM - arm7.
It only doesn't work when I compile with LLVM - arm6.
RE: Issue with the Apple LLVM compiler 3.0... - Frank C. - Dec 8, 2011 01:29 PM
I hear there are problems on armv6 when thumb is enabled and optimizations are set higher than -O0.
RE: Issue with the Apple LLVM compiler 3.0... - Jamie W - Dec 8, 2011 01:33 PM
Hi Frank,
I had it on optimization level 0 (debug). Anyhow, it turns out it is a bug in the ARM6 code generated by LLVM (relating to the indexes for accessing class variables). Have filed a bug report with Apple.
If it wasn't for older devices, I could just do away with ARM6. I wonder what % of active devices (people buying games) are ARM6 these days? Are there any stats on that?
RE: Issue with the Apple LLVM compiler 3.0... - OneSadCookie - Dec 8, 2011 04:43 PM
This wasn't thumb code by the way. The bug was to do with storing to an ivar more than some number of bytes into an object.